1. Field of the Invention
This invention relates in general to a road indication device for guiding and indicating positions on the road by light.
2. Description of Related Art
Generally, the road lamps for illuminating the road are lit according to the surrounding brightness to illuminate a predetermined range of the road. However, when the weather is bad such as snowfall, etc., the snow under the covered area of the road lamp is irradiated to create a light curtain, so that disability glare might occur.
In addition, at snowbound area, when the boundary between the road and the shoulder is buried by the fallen snow, the boundary might not be distinct. Therefore, arrow signs are used to indicate the boundary of the road for warning the drivers. In this way, a driver who drives a car can be made aware of the boundary of the road by the arrow signs arranged at a predetermined distance along the road while driving the car. However, when the weather is bad such as snowstorm, the visbility of the arrow sign is decreased, sufficient guiding indication is impossible.
Japanese Laid Open No. 2002-201617 (FIGS. 1–2, pages 2–3) discloses a method of setting the arrow sign and a laser irradiation device together. The leaser beam from the laser irradiation device is adapted for irradiating the boundary of the road. Since the laser beam irradiates the snow, the irradiated portion from the laser irradiation device to the road can be seen as a single light ray to guide and indicate the boundary of the road.
However, at least the inventor of the present invention does not know that using such laser beam to perform the guidance and indication during the bad weather such as the snowfall has not been implemented in practice. According to the study conducted by the inventor of the present invention, irradiating the laser beam from the laser irradiation device to the boundary of the road cannot obtain sufficient visibility in the bad weather such as the snowstorm because the light output of the laser beam is small and the laser beam is thin. In addition, the color of the laser beam is restricted and a suitable color for better visibility cannot be selected. Therefore, there is a problem that the degree of freedom of selecting the light color is small.
To obtain a light with sufficient visibility in the bad weather, such as, the snowfall using the laser beam, a huge laser device is required and therefore expensive. Therefore, it is very difficult to set the laser device providing sufficient light together with the arrow sign on the road. In addition, because the laser irradiation device is set outdoors, people might gaze the laser irradiation device and thereby adversely affecting human eyes.